A5055105288- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- X-ray Diffraction in Crystallography
- Crystallization and Solubility Studies
- Planetary Science and Exploration
- Astronomical Observations and Instrumentation
- Gamma-ray bursts and supernovae
- Geophysics and Gravity Measurements
- Geology and Paleoclimatology Research
- Galaxies: Formation, Evolution, Phenomena
- Oxidative Organic Chemistry Reactions
- Space Exploration and Technology
- History and Developments in Astronomy
- Spacecraft and Cryogenic Technologies
- Organometallic Complex Synthesis and Catalysis
- Advanced NMR Techniques and Applications
- Solar and Space Plasma Dynamics
- GNSS positioning and interference
- High-pressure geophysics and materials
- Catalytic Alkyne Reactions
Iowa State University
2020-2024
Heidelberg University
2022
Cornell University
2015-2019
Abstract We performed the largest and most homogeneous spectroscopic survey of field RR Lyraes (RRLs). secured ≈6300 high-resolution (HR, R ∼ 35,000) spectra for 143 RRLs (111 fundamental, RRab; 32 first-overtone, RRc). The atmospheric parameters were estimated by using traditional approach iron abundances measured an LTE line analysis. resulting distribution shows a well-defined metal-rich tail approaching solar abundance. This suggests that experienced complex chemical enrichment in early...
We performed a detailed spectroscopic analysis of three extremely metal-poor RR Lyrae stars, exploring uncharted territories at these low metallicities for this class stars. Using high-resolution spectra acquired with HARPS-N TNG, UVES VLT, and PEPSI LBT, employing Non-Local Thermodynamic Equilibrium (NLTE) spectral synthesis calculations, we provide abundance measurements Fe, Al, Mg, Ca, Ti, Mn, Sr. Our findings indicate that the stars have [Fe/H] = -3.40 \pm 0.05, -3.28 0.02, -2.77 0.05 HD...
We present newly-calibrated period-$\phi_{31}$-[Fe/H] relations for fundamental mode RR Lyrae stars in the optical and, first time, mid-infrared. This work's calibration dataset provides largest and most comprehensive span of parameter space to date with homogeneous metallicities from $-3<\textrm{[Fe/H]}<0.4$ accurate Fourier parameters derived 1980 ASAS-SN ($V$-band) 1083 WISE (NEOWISE extension, $W1$ $W2$ bands) well-sampled light curves. compare our those available literature demonstrate...
We performed a detailed spectroscopic analysis of three extremely metal-poor RR Lyrae stars, exploring uncharted territories at these low metallicities for this class stars. Using high-resolution spectra acquired with HARPS-N TNG, UVES VLT, and PEPSI LBT, employing Non-Local Thermodynamic Equilibrium (NLTE) spectral synthesis calculations, we provide abundance measurements Fe, Al, Mg, Ca, Ti, Mn, Sr. Our findings indicate that the stars have Fe/H = -3.40 ± 0.05, -3.28 0.02, -2.77 0.05 HD...
Abstract We provide the largest and most homogeneous sample of α -element (Mg, Ca, Ti) iron abundances for field RR Lyrae (RRLs; 162 variables) by using high-resolution spectra. The current measurements were complemented with similar available in literature 46 RRLs brought to our metallicity scale. ended up a old ( t ≥ 10 Gyr), low-mass stellar tracers (208 RRLs: 169 fundamental, 38 first overtone, 1 mixed mode) covering 3 dex abundance (−3.00 ≤ [Fe/H] 0.24). found that are ∼0.3 more poor...
We discuss the largest and most homogeneous spectroscopic dataset of field RR Lyrae variables (RRLs) available to date. estimated abundances using both high-resolution low-resolution ({\Delta S} method) spectra for fundamental (RRab) first overtone (RRc) RRLs. The iron 7,941 RRLs were supplemented with similar literature estimates available, ending up 9,015 (6,150 RRab, 2,865 RRc). metallicity distribution shows a mean value <[Fe/H]> = -1.51\pm0.01, {\sigma}(standard deviation)= 0.41 dex...
Stellar mergers and accretion events have been crucial in shaping the evolution of Milky Way (MW). These dynamically identified chemically characterised using red giants main-sequence stars. RR Lyrae (RRL) variables can play a role tracing early formation MW since they are ubiquitous, old (t$\ge$10 Gyr) low-mass stars accurate distance indicators. We exploited Data Release 3 GALAH survey to identify 78 field RRLs suitable for chemical analysis. Using synthetic spectra calculations, we...
ABSTRACT Accurate metallicities of RR Lyrae are extremely important in constraining period–luminosity–metallicity (PLZ) relationships, particularly the near-infrared. We analyse 69 high-resolution spectra Galactic stars from Southern African Large Telescope. measure 58 these with typical uncertainties 0.15 dex. All but one this sample has accurate ($\sigma _{\varpi }\lesssim 10{{\ \rm per\ cent}}$) parallax Gaia. Combining new spectroscopic abundances similar determinations literature for 93...
We present new period-$ϕ_{31}$-[Fe/H] relations for first overtone RRL stars (RRc), calibrated over a broad range of metallicities ($-2.5 < \textrm{[Fe/H]}< 0.0$) utilizing the largest currently available set Galactic halo field with homogeneous spectroscopic metallicities. Our are defined in optical (ASAS-SN $V$-band) and, inaugurally, infrared (WISE $W1$ and $W2$ bands). $V$-band relation can reproduce individual RRc dispersion 0.30 dex entire metallicity our calibrator sample (an...
We present new empirical infrared Period-Luminosity-Metallicity (PLZ) and Period-Wesenheit-Metallicity (PWZ) relations for RR Lyrae based on the latest Gaia EDR3 parallaxes. The are provided in WISE $W1$ $W2$ bands, as well $W(W1, V - W1)$ $W(W2, W2)$ Wesenheit magnitudes. calibrated using a very large sample of Galactic halo field stars with homogeneous spectroscopic [Fe/H] abundances (over 1,000 band), covering broad range metallicities ($-2.5 \lesssim \textrm{[Fe/H]} 0.0$). test...
Abstract We collected the largest spectroscopic catalog of RR Lyrae (RRLs) including ≈20,000 high-, medium-, and low-resolution spectra for ≈10,000 RRLs. provide analytical forms radial velocity curve (RVC) templates. These were built using 36 RRLs (31 fundamental—split into three period bins—and five first-overtone pulsators) with well-sampled RVCs based on groups metallic lines (Fe, Mg, Na) four Balmer (H α , H β γ δ ). tackled long-standing problem reference epoch to anchor light-curve...
Context . The Vera C. Rubin Observatory will start operations in 2025. During its first two years, too few visits per target band be available, meaning that the mean magnitude measurements of variable stars not precise and thus standard candles such as RR Lyrae (RRL) usable. Light curve templates (LCTs) can adopted to estimate a star with measurements, provided their period (plus amplitude reference epoch, depending on how LCT is applied) known. LSST provide RRL periods within six months,...
The Cassini RADAR altimeter has provided broad-scale surface topography data for Saturn's largest moon Titan. Herein, we adapt the delay/Doppler algorithm to take into account geometries and antenna mispointing usually occurring during hyperbolic Titan flybys. proposed allows up tenfold improvement in along-track resolution. Preliminary results are that show how improved presented herein can advance our understanding of Titan's characteristics.
Abstract We collected over 6000 high-resolution spectra of four dozen field RR Lyrae (RRL) variables pulsating either in the fundamental (39 RRab) or first overtone (9 RRc) mode. measured radial velocities (RVs) strong metallic and Balmer lines along entire pulsational cycle derived RV amplitudes with accuracies better than 1–2 km s −1 . The new were combined literature data for 23 RRab 3 RRc stars (total sample 74 RRLs), which allowed us to investigate variation Bailey diagram (photometric...
We present accurate and deep multi-band ($g,r,i$) photometry of the Local Group dwarf irregular galaxy NGC 6822. The images were collected with wide field cameras at 2m/4m- (INT,CTIO,CFHT) 8m-class telescopes (SUBARU) covering a 2 square degrees FoV across center galaxy. performed PSF $\approx$7,000 CCD final catalog includes more than 1 million objects. developed new approach to identify candidate stars, estimate by using old stellar tracers finding that it differs 1.15 (RA) 1.53 (DEC)...
The \textit{Vera C. Rubin} Observatory will start operations in 2025. During the first two years, too few visits per target band be available, meaning that mean magnitude measurements of variable stars not precise and thus, standard candles like RR Lyrae (RRL) usable. Light curve templates (LCTs) can adopted to estimate a star with measurements, provided their period (plus amplitude reference epoch, depending on how LCT is applied) known. LSST provide RRL periods within six months, allowing...
We present a protocol to synthesize air stable gem-diaurated gold(III) compounds from 1,3-diketones in single cycloauration step with tetrachloroauric acid. So far related species were only accessible phosphonium bis(ylide) ligands which hold the two gold atoms close proximity. Lacking such constraint, our show longest Au-Au distances of all carbons, ranging 3.26 3.32 Å. Modeling based on results CCSD(T) calculations shows no stabilization by aurophilic interactions for systems, compared 9.1...
We present our analysis of a large sample (over 150k) candidate Galactic RR Lyrae (RRL) stars for which we derived high quality photometry at UV, optical and infrared wavelengths, using data from publicly available surveys. For sub-sample these (~2,400 fundamental mode field RRLs) have measured their individual metallicity the Delta S method, resulting in largest most homogeneous spectroscopic set collected RRLs. use this to study distribution Halo, including long-standing problem Oosterhoff...
We present new empirical infrared Period-Luminosity-Metallicity (PLZ) and Period-Wesenheit-Metallicity (PWZ) relations for RR Lyrae based on the latest Gaia EDR3 parallaxes. The are provided in WISE $W1$ $W2$ bands, as well $W(W1, V - W1)$ $W(W2, W2)$ Wesenheit magnitudes. calibrated using a very large sample of Galactic halo field stars with homogeneous spectroscopic [Fe/H] abundances (over 1,000 band), covering broad range metallicities ($-2.5 \lesssim \textrm{[Fe/H]} 0.0$). test...